1. Field of the Invention
The present invention generally relates to a device for developing latent images in an image forming apparatus, such as a photocopy machine or laser printer. More particularly, the invention relates to a developing device which is capable of achieving a high-quality finished image using a one-component developing agent.
2. Description of the Related Art
U.S. Pat. No. 4,967,231 discloses an apparatus for forming an electro-photographic latent image. The apparatus employs an impression developing method which uses a one-component developing agent. Such a method requires the use of an elastic developing roller which has electrical conductivity. In the image forming process, the developing roller is maintained in contact with an image bearing member, such as a photosensitive body, and a blade for forming a thin toner layer on the developing roller. In addition, the frictional charge of the toner is effected by the friction created when the developing roller makes contact with a predetermined nip width with the blade.
Since the developing roller has elasticity in this developing method, the surface of the developing roller is distorted by the pressure contact of the blade. Particularly, the distortion of the surface of the developing roller increases when the developing roller stops. However, a certain length of time is required for the full recovery of the developing roller which has been distorted by the pressure contact of the blade. Thus, the developing operation may be performed before full recovery from the distortion of the surface of the developing roller. The distortion of the surface of the developing roller, thus, results in a poor reproduction of the image.